22 PHARMACEUTICAL BOTANY 
If some of the larger cells are now examined under high power 
magnification, each is found to be brick-shaped. Beneath the 
cell wall will be seen a narrow zone of cytoplasm containing 
numerous, green, ovoid, living bodies, the chloroplasts. Each 
chloroplast is a dense, porous, mass of protoplasm containing the 
green pigment or rather a mixture of four pigments two green 
and two yellow and collectively called chlorophyll. Chlorophyll 
is a highly complex and important material. By means of it, 
energy in the form of light from the sun is absorbed and utilized 
by the chloroplast for the manufacture of sugar. In some of the 
Fic. 13.—A typica: green cell of Elodea. Cy, cytoplasm; N, nucleus; N, 
nucleolus; C, chloroplast; Pm, outer plasma membrane; VM, vacuolar membrane; 
V, sap vacuole; W, cell wall; S, intercellular-air-space. Greatly magnified. 
cells the protoplasm will be found to be in motion (rotation), 
carrying the chloroplast along with it. The nucleus will be 
observed as a clear, dense, somewhat hemispherical shaped body 
embedded in the cytoplasm and surrounded by the _ nuclear 
membrane which separates it from the cytoplasm... A_ nucleolus 
will be seen within the nucleus. The center of the cell is occupied 
by a large sap vacuole containing a watery solution of salts and 
other nourishing substances. A clear vacuolar membrane lines the 
inner surface of the cytoplasm, while another clear membrane, 
the outer plasma membrane, lines the outer surface of the cytoplasm. 
If the leaf be boiled in water so as to kill the plasma mem- 
branes and make them permeable and then mounted in dilute 
iodine solution and examined under the microscope, bluish to 
bluish-black bodies will be observed in the chloroplasts. ‘These 
